SW3210602_Response To Comments_20210809

ERM
Telephone: [phone]
Fax: [phone]
Jim Farkus
NCDEQ Stormwater Program
512 N Salisbury St, 6th floor,
Raleigh, NC 27604
330 West Summit Ave Suite 330
Charlotte, NC
28203
August 05, 2021
Subject: Request for Additional Information
Stormwater Permit No. SW3210602
Blackburn Solar Point of Interconnect
Catawba County
Dear Mr. Farkus
www.erm.com
ERM received notice that the stormwater application for the Blackburn Solar Point of
Interconnect project, Stormwater Permit No. SW3210602 was not complete. Below is a list of
ERM responses to comments and information requests from NCDEQ.
1. Please indicate the county in which this project is located (Section 1, 2). The county is
currently listed as "NC".
ERM Response: County is now listed as "Catawba" in Section I, 2 on page 1. Updated
page 1 has been provided.
2. Please list the correct major river basin that this project is located within (Section IV, 3).
The river basin shown in this section of the application should be one of the 17 major
river basins located throughout North Carolina (which can be found here:
https://ncdenr maps. arcgis. com/apps/Publiclnformation/index. html?appid=ad3a 85aOc6d6
44aOb97cd069db238ac3). This project appears to be located within the Catawba River
Basin.
ERM Response: The river basin is now listed as "Catawba" in Section IV, 3 on page 3.
Update page 3 has been provided.
3. Please include a USGS topographic map clearly showing the extent of the project area
(Section VI, 6). It is noted that there was a survey map and some maps showing the
project area, however we require a USGS topographic map showing the project area (The
reasoning behind this is that the USGS topographic map is used to determine if there are
any surface waters located within the project area).
ERM Response: USGS topographic map has been added to calculations package (BB1
POI — Stormwater Cays—Rev1).
4. Please provide calculations showing that the riprap placed downstream of the culverts has
been adequately sized to prevent erosion during the 10-year storm (Section VI, 7). Design
charts for riprap apron sizing can be found in the Erosion and Sediment Control Planning
and Design Manual (https://deq.nc.govlabout/divisions/energy-mineral-land-resourceslenergy-
min eral-lan d-permit-guidan ce%rosion-sediment-control-planning-design-manual).
ERM Response: Outlet apron calculations have been added to calculations package
(BB1 POI — Stormwater Cays—Rev1).
5. Please show the surface area and required vegetated setbacks for the on -site surface
Page 1 of 3
ERM A member of the
330 West Summit Ave Suite 330 ERM Group
Charlotte, NC
28203

ERM I Page 2 of 3
waters in the main set of plans (Section VI, 8h & p). It is noted that the on -site surface
water is shown on plan sheet BB 1-D-P002-CVR, however the surface area (it is not
practical to delineate the banks of the stream at this scale so you can just indicate the
surface area of the surface water as a callout) and required vegetated buffer (as required
per 15A NCAC 02H .1003(4) & .1017(10)) are not shown.
ERM Response: Surface water area and vegetated setback callouts have been added to
the property map on BB1-D-P002-CVR Rev 1.
6. Please dimension the project area boundary with bearings and distances (Section VI, 8i).
ERM Response: Bearings and distances have been added to the property map on BB1-
D-PO02-CVR Rev 1.
7. Please identify the surface area of all on -site BUA (Section VI, 8j). The surface area
information shown in the application/supplement form of all proposed BUA should be
able to be verified on the plans. Certain regular geometric shapes (such as the switchyard
pad) can be verified solely based on the provided dimensions whereas areas of irregular
shapes (such as the access road) cannot easily be determined solely from the provided
plans. You may wish to provided surface area callouts, add surface areas to existing
callouts, or add a table, similar to the one in Section IV, 10 of the application.
ERM Response: Built Upon Area (BUA) callouts have been added to sheet BB1-D-P002-
1 Rev 1.
8. Per the information shown in the Supplement-EZ Form, some of the vegetated
conveyances have side slopes of 4:1 whereas the detail on plan sheet BB1-D-P002-5 only
indicates ditches with 3:1 side slopes. Please adjust this detail to indicate the various
cross -slopes that will be used and indicate which ditches will have which cross -slopes
(Section VI, 8I).
ERM Response: Vegetated conveyance callouts and notes have been added to sheet
BB1-D-P002-1, as well as the TYPICAL FLAT BOTTOM DITCH SECTION DETAIL on BB1-
D-PO02-5 Rev 1.
9. Please provide official documentation showing that Mr. Stempowski can sign on behalf
of the applicant, Blackburn Solar, LLC (Section VI 11). Since Mr. Stempowski's name is
not listed in the Secretary of State documentation, you need to provide some form of
additional documentation showing Mr. Stempowski's position/signing authority within
Blackburn Solar, LLC and/or ESI Energy, LLC.
ERM Response: Stormwater application form has been updated and signed by Melissa
Plotsky, Secretary of Blackburn Solar, LLC. Original and one (1) copy have been
submitted to NCDEQ.
10. Please correct the following issues with the Supplement-EZ Form:
a. Cover Page:
i. Line 7 — Vegetated setbacks are required from all surface waters in
accordance with 15A NCA C 02H .1003(4) & .1017(10).
ERM Response: Supplement-EZ form has been updated.
ERM A member of the
330 West Summit Ave Suite 330 ERM Group
Charlotte, NC
28203

ERM I Page 3 of 3
b. Low -Density Page:
i. Pervious Area Column — The information in this column appears to be
incorrect (It appears as though the information from the "BUA" column
was duplicated in this column).
ERM Response: Supplement-EZ form has been updated.
ii. Ditch 1 — The provided calculations indicate that the flowrate in this ditch
is 1.0 cfs whereas the Supplement-EZ Form indicates that the flow is 4.9
cfs. Please revise either as needed for consistency (It appears as though the
intensity is incorrect in the calculations).
ERM Response: Calculations have been updated.
iii. Ditch 3 — The provided calculations indicate that the flowrate in this ditch
is 4.7 cfs whereas the Supplement-EZ Form indicates that the flow is 4.9
cfs. Please revise either as needed for consistency.
ERM Response: Calculations have been updated.
11. Provide pdfs of all revisions, 2 hardcopies of revised plan sheets, 1 hardcopy of other
documents, and a response to comments letter briefly describing how the comments have
been addressed.
ERM Response: Hardcopies of plan sheets, calculations and revised Supplement-EZ
form have been sent to NCDEQ. Updated application form is included with this
response letter (One (1) original and one (1) copy).
Chris Mettler P.E.
Associate Engineer
ERM
CC:
ERM A member of the
330 West Summit Ave Suite 330 ERM Group
Charlotte, NC
28203